This invention relates to the discovery and asexual propagation of a new variety of grapevine, Vitis vinifera cv. `Sugrafifteen`. The new variety was first created in May, 1988 by David W. Cain near Wasco, Kern County, Calif., the variety being originated by a controlled cross. The new variety is characterized by its extremely firm, yellow-green, round to obovate berries which are tenaciously attached to a strong and well lignified rachis.
The seed parent of the new variety is the `Dawn Seedless` variety (U.S. Plant Pat. No. 4,788). The pollen parent is the `Flame Seedless` variety (unpatented). The parent varieties were first crossed in May, 1988, and first flowering of the new variety was in May, 1990. The new variety was first asexually propagated by David W. Cain in 1990 in Wasco, Kern County, Calif., using hardwood cuttings.
The new grapevine variety cv. `Sugrafifteen` most nearly resembles its parent varieties, the `Flame Seedless` and `Dawn Seedless` varieties. It differs from the `Flame Seedless` variety by producing fruits of a yellow-green color in contrast to the red coloration of `Flame Seedless`. It differs from the `Dawn Seedless` and `Perlette` (unpatented) varieties by possessing larger, much firmer, more uniform berries that are later ripening and that are more responsive to gibberellic acid treatments. Berries of the new variety become more yellow in color as they mature than berries of the `Dawn Seedless` variety. The new variety also has a much more highly lignified, stronger rachis structure with a more well matured woody peduncle than the `Dawn Seedless`.
The new variety differs from the `Sugraone` variety (U.S. Plant Pat. No. 3,106) by producing later ripening berries that are much more uniform in size, more yellow in color, and firmer. They also exhibit less phytotoxic effects from, and are more responsive to, gibberellic acid applications than `Sugraone`. The vine of the new variety is less vigorous than the `Sugraone` and exhibits much less axillary branching than `Sugraone`. It is extremely productive and may be pruned to two bud spurs.
The new variety differs from other commonly grown white seedless grapes such as the `Thompson Seedless` (unpatented), `Centennial Seedless` (U.S. Plant Pat. No. 4,784) and `King Husany` (U.S. Plant Pat. No. 6,464) varieties, by possessing much less elongated and more nearly round berries of much firmer flesh texture, which have much stronger attachment to the rachis.
The new `Sugrafifteen` variety has been shown to maintain its distinguishing characteristics through successive asexual propagations by, for example, cuttings.